We always felt the need of Hardware capacity guidance and sizing information for Terminal Services or Remote Desktop services for Server 2008 R2, Whenever I am engaged in any architectural guidance discussion for RDS deployment i always get a question what needs to be taken into consideration while deciding the hardware configuration and to do capacity planning.
Here are some bullet points which I recommend to my partners and customers to consider:
- 2GB Memory (RAM) is the optimum limit for each core of a CPU. E.g. If you have 4 GB RAM then for optimum performance there should be Dual core CPU.
- 2 Dual Core CPU perform better then single Quad core processor.
- Recommended bandwidth for LAN of 30 users and WAN of 20 users. Bandwidth (b) = 100 megabits per second (Mbps) with Latency (l) Less than 5 milliseconds.
- On a Terminal Server 64 MB per user is the Ideal Memory (RAM) requirement for GP Only use + 2 GB for OS E.g. (100 users * 64) + 2000 = 8.4 GB i.e. 8GB RAM.
- More applications used (i.e. Office, CAD Apps and etc.) will require more memory per user to be added to this calculation over the 64 MB base memory per user.
- 15 TS session per CPU core is the optimum performance limit of a Terminal Server.
- Network should not have more than 5 hops, and latency should be under 100ms.
- 64 kbps is the Ideal Bandwidth per user session. (256 color, switched network, bitmap caching only)
- CPU performance degrades if %processor time per core is constantly above 65%.
- Terminal servers performance doubles when it is running on a X64 HW and OS.
In addition to that, Microsoft has just released a whitepaper on Capacity Planning in Windows Server 2008 R2.
The Remote Desktop Session Host (RD Session Host) role service lets multiple concurrent users run Windows®-based applications on a remote computer running Windows Server® 2008 R2. This white paper is intended as a guide for capacity planning of RD Session Host in Windows Server 2008 R2. It describes the most relevant factors that influence the capacity of a given deployment, methodologies to evaluate capacity for specific deployments, and a set of experimental results for different combinations of usage scenarios and hardware configurations.
You can also use this document for sizing Terminal Services on a Hyper V Platform
Also use the Remote Desktop Load Simulation Tools available at following link to do the load testing for number of users on RDS Server
I hope it helps, Let me know if you have any questions.